Miniature digital microphones are known and offer many benefits such as providing better signal-to-noise ratio and RF immunity than their analog counterparts on a system level making the digital microphones interesting and attractive for numerous applications such as portable communication devices including cellular phones and smartphones etc. Portable communication devices are compact devices which are powered from rechargeable battery sources. The compact dimensions and reliance on battery sources both impart severe constraints on the maximum acceptable dimensions and power consumption of microphones and microphone amplification circuit utilized in such portable communication devices.
Furthermore, microphones disposed in portable communication devices often comprise a standardized data interface to the host processor of the communication device to ensure compatibility with this interface.
However, known digital microphones add a significant time delay or latency to the sound signal picked-up by the microphone transducer. This time delay is typically imparted by various digital processing circuits of the microphone such as sigma-delta converters (ΣΔ) and their associated noise-shaping and decimation filters, data interface handling etc.
The time delay or latency added to the audio signal by known digital microphones represents a significant problem for numerous types of applications in portable communication devices such as automatic noise cancellation, feedback suppression, echo cancellation etc.